The 20-member panel did vote unanimously, with one abstention, to back the scientific findings on 11 antiepileptic drugs studied by the U.S. Food and Drug Administration.

In late January, the FDA announced it was considering a black box warning after an agency review of 199 studies comparing the drugs, which are used by millions, to placebos. That review found that patients taking the drugs had about twice the risk of suicidal behavior compared with patients taking a placebo.

"We have concluded this was a real signal, and the signal applied to all drugs we studied," Dr. Russell Katz, director of the division of neurology products at the FDA's Center for Drug Evaluation and Research, told reporters at a late-afternoon teleconference Thursday.

"We propose that labels for all these antiepileptic drugs be changed to include a box warning, and patients should be given a medication guide describing these events with each prescription refill," he said.

On Thursday, the advisory panel appeared to agree with him -- up to a point. It voted in favor of sending a medication guide to doctors detailing the suicide risks.

But a majority of panel members voted against adding the black box warning, saying the studies didn't show a high enough risk for suicidal behavior.

"The general view of the committee was concern that patients or physicians would not prescribe these drugs in certain circumstances where they should," Katz said. "The committee voted 14 'no, it should not be described in a box warning, although it should be described in the label somewhere.' There were four 'yes' votes and three abstentions."

Whether the FDA will follow the committee's recommendation against a black box warning will be a matter of discussion, Katz added.

"We take the committee's recommendations very seriously," he said.

The drugs reviewed by the FDA were: Carbamazepine (marketed as Carbatrol, Equetro, Tegretol, Tegretol XR), Felbamate (marketed as Felbatol), Gabapentin (marketed as Neurontin), Lamotrigine (marketed as Lamictal), Levetiracetam (marketed as Keppra), Oxcarbazepine (marketed as Trileptal), Pregabalin (marketed as Lyrica), Tiagabine (marketed as Gabitril), Topiramate (marketed as Topamax), Valproate (marketed as Depakote, Depakote ER, Depakene, Depacon) and Zonisamide (marketed as Zonegran). Some of these drugs are also available as generics.

According to the FDA, antiepileptic drugs are used to treat epilepsy, bipolar disorder, migraine headaches and other conditions.

In January, the FDA was advising patients not to make any changes in their medication without talking to their doctor.

"Caregivers should pay close attention to changes in mood, behavior and actions," FDA spokeswoman Sandy Walsh said at the time. "They should be aware of the development of these symptoms."